Modern fixed structure control design part I: Gain adjustment to improve handling qualities

The problem of gain adjustment in an existing control law is cast into the framework of modern control theory, which results in a real-diagonal block structure of gains to be adjusted. The desire to recover performance in the form of input-output properties, as well as handling qualities, is introduced as a mixed cost functional. LMI-based solutions for H∞and H2based optimization are discussed, as well as a Quasi-Newton approach. The handling qualities of the F/A-18 HARV during refueling serves as a motivating example for the method. Five gains in the existing flight control system are adjusted to recover the performance and handling qualities of the standard F/A-18.